That must be a state thing, Bud. There could be the case that the crane company interprets their own policy as the same as an OSHA one that might not really exist in your state. I would make further enquiries to verify.
According to the literature put out by Mark Adams, OSHA typically looks at the nationwide ANSI regulations, WHICH ALLOW IT with specifics on the attachment points. The hook as the sole attachment point is not allowed by the regs. OSHA may have different standards and supersede ANSI crane regs in some states, a bit stricter in California on having two attachment points, for example, and one is the hook. The big catch is that state, local, or company regulations may be stricter than ANSI, and if that is the case, you are supposed to follow them, which seems to also mean you can't do it at all in some places, or when working for or with some companies.
I guess it also means that if a particular crane outfit has their own policy, it comes first before ANSI or OSHA, IF STRICTER. If the state OSHA allows it via their own regs or based on ANSI, and there aren't any other local regs that don't, I would look for another crane outfit that follows those standards without having their own stricter policy.
In some places where OSHA doesn't allow riding the ball, the regs also say, "unless there is no other safe alternative", or something along those lines. A potential loophole, especially for storm work, if a crane outfit would go for it.